西南交通大学学报

On New Generation Traction Power Supply System and Its Key Technologies for Electrification Railway

LI Qunzhan

2014, 27(4): 559-568. doi: 10.3969/j.issn.0258-2724.2014.04.001

[Abstract](1340)

Abstract:
Unlike the traditional traction power supply system which enables the electrified railway traction substation to be connected to power grid in a way of phase rotation, a new generation traction power supply system without phase splits in power grid was proposed. Three key technologies of this system were discussed. First, the combined cophase traction power supply system was used for traction substation to realize negative sequence current control and eliminate phase split at the exit of substation. Second, new bilateral power supply technology was applied to eliminate the phase split at section post and reduce the influence of balance current on power grid. Meanwhile, power factor should be adjusted to ensure the voltage level of traction network. Third, the segment power supply and measurement control technology was used to divide the supply section into several segments and apply synchronous measurement technology to quickly and accurately diagnose fault and its location. Thus, the effects of faults can be limited to a minimum degree. Also, the economy and reliability of new generation traction power supply system were analyzed.

Dynamic Compensation Strategy of Inductive Power Transfer System with Inductive-Resistive Load

HE Zhengyou, LI Yong, MAI Ruikun, LI Yanling

2014, 27(4): 569-575,589. doi: 10.3969/j.issn.0258-2724.2014.04.002

[Abstract](1083)

Abstract:
The equivalent inductive impedance of the rectifier load will lead to a detuned IPT(Inductive Power Transfer) system. In order to maintain resonance frequency, a dynamic compensation scheme was proposed. This scheme utilizes short-time Fourier transformation to obtain the current and voltage phasors, and then calculates the impedance. It can dynamically adjust the equivalent capacitance value of the capacitor array by turning off or on the static switches, and realize load inductance compensation. The experiments were performed to compare the performance between the frequency tracking method and the proposed algorithm under rectified load. The result shows that with 100 and 50 Ω load resistances, the proposed algorithm can increase the real power by 12.1% and 7.3%. Moreover, the resonance frequency of the primary circuit can be maintained and the switching devices can work under a ZCS (Zero Current Switching) condition.

Design of Balance Traction Transformer Capacity in Co-phase Traction Power Supply System

XIE Shaofeng, LI Qunzhan

2014, 27(4): 576-581. doi: 10.3969/j.issn.0258-2724.2014.04.003

[Abstract](1019)

Abstract:
To provide a theoretical foundation for selecting traction transformer capacity in co-phase traction power supply system, the difference between the feeder current of the co-phase traction power supply system and existing traction power supply system was analyzed. The design methods of traction transformer capacity for two cases of existing railways electrification and new railways construction were proposed. The results of case study show that the proposed methods can decrease 1-2 capacity grade of traction transformer for both cases and the economy of traction power supply system is significantly improved.

Harmonic Resonance of AT Power Supply System of High Speed Railway Based on Train-Network Coupling

HAN Xudong, WANG Bin, GAO Shibin, CHEN Minwu

2014, 27(4): 582-589. doi: 10.3969/j.issn.0258-2724.2014.04.004

[Abstract](1337)

Abstract:
To study the harmonic resonance caused by the electrical coupling between high speed train and AT power supply system, a mathematic model of AT power supply system of high speed railway based on nodal admittance equation and a harmonic model of high speed train based on the power source characteristic and the equivalent impedance were built. The evaluation algorithm for the harmonic resonance of AT power supply system of high speed railway based on train-network coupling was propsed. The effect on the harmonic resonance of three AT models, three traction network operation modes and different leakage impedances were discussed, and their impedance-frequency and phase-frequency characteristics were analyzed. The variation rules of parallel and series resonant points were summarized. Simulation results show that three AT modes have different parallel and series resonant points, and different power supply models lead to the shift of resonant points. The increasing of AT transformer leakage resistance causes more resonance points and lower frequency at first series resonant point.

Acquisition of Part-Whole Relations Based on Unsupervised Learning

JIA Zhen, HE Dake, YIN Hongfeng, LI Tianrui

2014, 27(4): 590-596. doi: 10.3969/j.issn.0258-2724.2014.04.005

[Abstract](941)

Abstract:
An unsupervised learning method was proposed to solve the problem of part-whole relation extraction from Chinese free texts. A subsequence extraction algorithm was firstly introduced that can acquire concept pairs and their context patterns from domain texts, and a distributional semantic model was constructed according to concept pairs and context patterns of concept pairs. Then a co-clustering algorithm was applied to group the concept pairs with the same semantic relations together. L1 regularized logistic regression model was trained to select clustering feature and obtain the context pattern which represents semantic relation of each cluster. At last, according to the patterns, the clusters expressing part-whole relation were identified and part-whole relation concept pairs were acquired. The experimental results indicate the proposed method is effective and its F measure is up to 68.97% which is superior to the traditional clustering (55.77%) and pattern matching methods(61.95%).

Hyperspectral Sparse Unmixing via Adaptive Overcomplete Dictionary Learning

WANG Rui, LI Hengchao, YIN Zhongke

2014, 27(4): 597-604. doi: 10.3969/j.issn.0258-2724.2014.04.006

[Abstract](1251)

Abstract:
In the linear sparse unmixing model of hyperspectral data, large estimation error of the fractional abundances of endmembers in each mixed pixel may be caused by the incorrect identification of endmembers. A novel sparse unmixing algorithm was proposed based on adaptive overcomplete dictionary. Firstly, according to the spatial continuity of ground objects and the strong correlation between signal components of the hyperspectral data and spectral signatures in the library, the signatures with the projection coefficients of each pixels larger than the preset threshold were grouped as an optimal subset of signatures that best match the signal component of each mixed pixel. Secondly, an adaptive overcomplete dictionary of hyperspectral data was constructed by combining such subsets. Finally, the fractional abundances in this dictionary were obtained using the alternating direction method of multipliers (ADMM). Experimental results on synthetic and real hyperspectral data show that the proposed algorithm improves the accuracy of identifying endmembers, with the reduced abundance estimation error r. When the signal to noise ratio range from 15 to 35 dB, the accuracy of the abundance estimation is improved about 1 to 2 dB compared with SUnSAL (sparse unmixing by variable splitting and augmented Lagrangian).

Load-Bearing Mechanism and Yield Load of PBL Shear Connectors

ZHAO Canhui, XIA Song, LI Qiao

2014, 27(4): 605-611. doi: 10.3969/j.issn.0258-2724.2014.04.007

[Abstract](827)

Abstract:
In order to study the deformability of Perfobond Leiste (PBL) shear connectors, a series of tests were conducted to investigate the load-bearing mechanism and deformability influence factors of PBL shear connectors. In these tests, 33 specimens divided into 4 types and 9 groups were loaded, and the external loads, deformation, and failure pattern of the specimens were probed. On this basis, the yield load of the PBL shear connector was defined, and a formula for yield load calculation was proposed. The results show that the deformation behavior of PBL connectors can be divided into the pseudo-elastic stage, the elasto-plastic stage, and the yield stage; and the yield is due to the shear fracture of concrete column. The slide at the yield point is about 1.2 mm. Load is carried by concrete column and transverse steel bar in the pseudo-elastic stage and elasto-plastic stage, but only by transverse steel bar in the yield stage. Therefore, the diameter and strength of the transverse steel bar and the diameter of concrete column are the main factors influencing the deformation behavior of PBL shear connectors, and the diameter of the transverse steel bar should be more than 16 mm.

Measurement and Theoretical Analysis of Vehicle-Induced Vibration on Elevated Railway Station

LI Xiaozhen, LIU Quanmin, ZHANG Xun, ZHANG Zhijun

2014, 27(4): 612-618. doi: 10.3969/j.issn.0258-2724.2014.04.008

[Abstract](1008)

Abstract:
In order to study the environmental vibration in different regions of elevated stations, measuring points for measuring the vibration in three directions (x, y, and z) were deployed to the mid-span of track beam, office, and waiting room of an elevated station in a passenger dedicated railway. When high-speed EMUs (electric multiple units) passed the elevated station at the main line speed, the environmental vibration in different regions of the station was tested, and experimental data on the time histories, levels, and frequency spectra of vibration accelerations were analyzed. According to the vehicle-track-bridge coupling theory, the dynamic response of the track beam and the running performance of trains were investigated. The results show that the Z-weighted vibration level of the office reaches 80.7 dB, 0.7 dB higher than the code limit; and the vertical vibration dominates the environmental vibration of the elevated station. The duration of the vertical vibration at office center is 15% longer than that of the horizontal vibration; and the duration of the horizontal vibration of the waiting room is 1.03 s longer than that of the track beam. In addition, the high-frequency vibration attenuates faster than the low-frequency vibration during the propagation from the track beam to the station floor.

Numerical Simulation Analysis of Steel-Concrete Joint Section in Hybrid Girder of Cable-Stayed Bridge

ZHANG Jingfeng, LI Xiaozhen, XIAO Lin, BAO Yuwen

2014, 27(4): 619-625,699. doi: 10.3969/j.issn.0258-2724.2014.04.009

[Abstract](1174)

Abstract:
To investigate the mechanical behavior of steel-concrete joint section of cable-stayed bridge, ANSYS, a general finite element package, was used to analyze the nonlinear numerical simulation of the joint section mechanics behavior of Wusu bridge in Heixiazi Island. In the analysis, the nonlinear characters of structure and material were taken into account, and nonlinear spring elements were employed to simulate the bond-slip effect of studs. The analysis results based on nonlinear spring elements were compared with the ones obtained using linear spring elements. The numerical analysis results show that as studs are simulated by nonlinear spring elements, numerical results agree well with the model test ones. The linear and nonlinear stud models make little difference between the calculation results under the design load. Different stud mechanics models will induce a significant effect on the initial propagation pattern of cracks in the concrete of joint section, while there exist a few difference about the distribution of crack after most cracks happen.

Long-Term Random Deflection of Eccentrically Loaded RC Column

XU Tengfei, XIANG Tianyu, ZHAO Renda

2014, 27(4): 626-630. doi: 10.3969/j.issn.0258-2724.2014.04.010

[Abstract](1021)

Abstract:
Owing to the randomness of shrinkage and creep of concrete, random analysis method should be adopted to provide probabilistic guarantee for the analysis of concrete long-term random deflection. Stochastic variables for the long-term analysis with GL2000 model about creep and shrinkage of concrete were presented. Combining Monte Carlo sampling with the response surface method, the stochastic analysis model was established, which is on time-variant deflection of concrete structure. The long-term deflection of reinforce concrete (RC) columns were analyzed using this model. The influences of tensile strength of concrete on long-term deflection of RC columns were considered. The case study shows that when eccentricity ratio is increased to 1.0, the sensitivity of tensile strength reaches a peak of near 0.6 and then decreases gradually. Afterwards, when eccentricity ratio is 1.6, the sensitivity value is reduced to zero. The tensile strength of concrete has no effect on long-term deflection of columns prior to the crack of concrete. With the increase of eccentricity ratio, the effects of tensile strength of concrete will grow to peak and drop down gradually.

Transfer Matrix Method of Beam-Column Transient Analysis Considering Second-Order Effect

SHAO Junhu, XIANG Tianyu, ZHAO Renda

2014, 27(4): 631-636. doi: 10.3969/j.issn.0258-2724.2014.04.011

[Abstract](898)

Abstract:
Second-order effect of a compression-bending member under a high axial force will influence the stiffness and dynamic characteristics of a structure, so a transfer matrix method was proposed to calculate the transient response of beam-column with considering the second-order effect. With this method, the dynamic partial differential equations for Euler-Bernoulli beam are discretized in time domain with the Newmark-β method and transformed into an ordinary differential equation; the differential equation is solved with the variation of constants method to obtain the analytical solution of displacement increment in continuous space domain. Based on the principle of the transfer matrix method, an incremental transfer matrix for discrete-time transient analysis is derived, and a corresponding algorithm was proposed for the transient analysis considering the second-order effect. The numerical results indicate that under the same calculation accuracy, computational efficiency of the proposed method is 3.57 times that of finite element software ANSYS, and the dynamic responses of a structure subjected to a moving load can be obtained easily.

Static Mechanics Impact Analysis of Newly-Built Tunnel beneath Existing Tunnel Based on Extenics Theory

LENG Biao, QIU Wenge, GONG Lun

2014, 27(4): 637-641. doi: 10.3969/j.issn.0258-2724.2014.04.012

[Abstract](880)

Abstract:
In order to discuss the static mechanics impact degree of a newly-built below-crossing tunnel on an existing tunnel, the extenics matter-element theory was applied. An evaluating model about the static mechanics impact degree was established by considering the relationship between the newly-built tunnel and the existing tunnel, including the principal elements of existing tunnel's radius, newly-built tunnel's radius, net distance between the two tunnels, surrounding rock grade and existing tunnel depth. In addition, the evaluating result for a project example based on this model was compared with its actual effect. The comparison result shows that the established model is able to satisfy the practical projects' needs, so it can be used to the qualitative analysis and quantitative evaluation towards the static mechanics impact of below-crossing tunnel.

Vortex-Induced Fatigue Damage Analysis of Submerged Floating Tunnel Cable

LUO Gang, ZHOU Xiaojun

2014, 27(4): 642-648. doi: 10.3969/j.issn.0258-2724.2014.04.013

[Abstract](999)

Abstract:
In order to assess the vortex-induced fatigue damage on cables of submerged floating tunnel, the Blevins lift model and Vengugopal drag model were introduced to calculate the lift coefficient and dimensionless amplitude by modal superposition method, taking into account the influence of the additional mass on the dynamic characteristics of the cable in Hamilton's principle. Then, the vortex-induced fatigue damage of the cable was calculated by Fatigue cumulative damage theory and S-N fatigue curve. The results show that when the mass ratio is low (m*m*>10), however, the impact can be ignored. When the slenderness ratio of the cable is above 100, the vortex-induced vibration is in a multimodal resonance state. The vortex-induced fatigue damage on the cable can be calculated accurately by the proposed method, and the calculated results in a case study has an error of less than 5% compared with the experimental results.

Adaptability of Continuous Welded Rail of Unit Slab Non-ballast Track on Bridges

XIE Kaize, WANG Ping, XU Jingmang, XU Hao

2014, 27(4): 649-655. doi: 10.3969/j.issn.0258-2724.2014.04.014

[Abstract](895)

Abstract:
To investigate the reasonable limit value of the distance between two fixed bearings of a continuous beam bridge on which unit slab non-ballast track was layed, a rail-slab-bridge-pier integrated model was established by the finite element method. In conditions of different rail temperatures, the influence of bridge temperature change, the lateral displacement at the top of pier, and train braking on the limit value of the distance between two fixed bearings of the continuous beam bridge was analyzed. The results show that the limit value decreases with an increase in the amplitude of rail temperature variation. Taking the rail temperature variation of 40 ℃ for example, the limit value is 271 m due to the requirements of rail strength, transverse bending deformation, and the relative displacement between rail and slab. With the increase of the lateral displacement at the top of pier, the limit value decreases significantly. When the displacement is 30 mm, the limit value is 237 m. When the displacement is more than 30 mm, the limit value should be calculated in dependence on the actual displacement at the top of pier. In addition, the track gradient has little influence on the limit value under braking load condition: When the track gradient is 20‰, the limit value is 258 m.

Optimization Algorithm for Horizontal Realignment Based on Coordinate of Metro Centerline

SONG Zhanfeng, PENG Xin, WU Qinghua

2014, 27(4): 656-661. doi: 10.3969/j.issn.0258-2724.2014.04.015

[Abstract](887)

Abstract:
Alignment parameters were estimated and optimized to deal with the subway beyond-limit problem based on the coordinates of tunnelling centerline. Based on the coordinate of metro centerline, the capability of dealing with complicated beyond-limit situations can be enhanced greatly by estimating and optimizing the alignment parameters to satisfy the design constraints. The theory of realigning the design centerline to control the borders beyond-limit was expounded, and a realignment optimization model including objective function and constraints was put forward. Alignment fitting segments composed of line and circular curve were made on the basis of beyond-limit threshold using the orthogonal least squares. Furthermore, an optimization algorithm was put forward to combine these segments appropriately to produce an initial alignment. By optimizing the fitting segment points iteratively, an optimized alignment fitting the tunnel trajectory best and satisfying the design specifications and invasion threshold requirements was obtained. Finally, examples were given to prove the effectiveness of the algorithm. The research results indicate that the algorithm can not only optimize the metro horizontal realignment, but also effectively estimate the existing line parameters.

Limit Equilibrium Method of Slope Stability Analysis Considering Spatial Variability of Soil Properties

BAI Tao, HUANG Xiaoming

2014, 27(4): 662-667. doi: 10.3969/j.issn.0258-2724.2014.04.016

[Abstract](996)

Abstract:
In order to evaluate the adaptability of the limit equilibrium method (LEM) to assess the stability of spatially variable soil slope, stability analysis of slope sections was conducted using the LEM (limit equilibrium method) considering the spatial variability of soil property. The Karhunen-Loève (K-L) method was adopted to generate the spatial samples of soil slope, i.e., random fields. The Fellenius method, the simplified Bishop method, the Morgenstern-Price method and the Spencer method were utilized to calculate the safety factors of the slope sections. In addition, the failure probability of a given slope was analyzed. The calculated results show that the safety factors calculated with the later three methods are very close to each other. And basically, they are much better than the Fellenius method. For simplicity, the Bishop method can take the place of the Morgenstern-Price method under the condition that the critical slip surface is circular. The combined use of safety factor and failure probability can evaluate slope safety more quantitatively.

Self-Organized Criticality in Process of Aftershocks of Lushan Earthquake

LIU Chunqiong, SHI Kai, LI Sichuan

2014, 27(4): 668-674. doi: 10.3969/j.issn.0258-2724.2014.04.017

[Abstract](895)

Abstract:
The statistical relations of aftershocks following a strong earthquake can give useful information on the dynamical features of seismic processes and the involved geodynamical mechanisms. The sequence of aftershocks of the Lushan Ms7.0 earthquake, occurred on the Longmenshan tectonic zone in Sichuan Province, China, was analyzed. The analyses of magnitude and temporal statistical distributions in the aftershocks sequence described by the Gutenberg-Richter and Omori laws respectively were performed. To provide a possible explanation of these observed distributions, a novel SOC (self-organized criticality) model was developed by introducing stress decay coefficient and anisotropic diffusion factor into the Olami-Feder-Christensen model of earthquakes, and the self-organized criticality properties of this novel model were discussed. The research result shows that the aftershocks of the Lushan Earthquake follow the Gutenberg-Richter and Omori laws, and the power exponents are about 0.766 and 2.52 respectively. The developed model can give a good prediction of the Gutenberg-Richter and Omori laws in Lushan aftershocks together. And simulated results and observations have a high correspondence to indicate that Lushan aftershock is an example of an SOC process.

Mechanical Responses of Pavement under Aircrafts with Different Main Landing Gears

ZHANG Xianmin, DONG Qian, LÜ, Yaozhi

2014, 27(4): 675-681. doi: 10.3969/j.issn.0258-2724.2014.04.018

[Abstract](1107)

Abstract:
In order to provide a theoretical basis for the optimal design of aircraft and pavement, a finite element model of runway was established based on the elastic layered theory to analyze the mechanical responses caused by changing main landing gears. Two sets of aircrafts with the same loads level but different in main landing gear configurations were chosen. The simulation results show that the change of main landing gear configurations influences dramatically on mechanical responses in loading areas. In the condition that aircraft loads are equal, increasing of the total number of wheels on main landing gears will decrease vertical displacement peaks and tensile stresses on panel bottom, the difference of vertical displacement peaks is up to 13% and the difference of tensile stresses on panel bottom is up to 35%. When the spacing between main landing gears is small, displacement curves for the loading areas are gentle and strains in the loading areas are small, but response depth on soil base is large. The difference of strains is up to 12% and the difference of response depth on soil base is up to 14%. The change of the configurations has little effect on vertical displacements far away from loading areas.

Numerical Analysis of Dynamic Strain and Fatigue Characteristics of Asphalt Layer Considering Interlayer Condition

HUANG Bing, AI Changfa, YANG Enhui, CHENG Meng

2014, 27(4): 682-686. doi: 10.3969/j.issn.0258-2724.2014.04.019

[Abstract](825)

Abstract:
In order to determine the relationship between the fatigue life of asphalt layer and its influencing factors such as interlayer contact state, temperature, and axle load, a numerical calculation model of asphalt pavement was built based on the interlayer conditions by using the ABAQUS software. Through this model, the influence of these factors on the dynamic strain of the asphalt layer was analyzed. Then, the conventional fatigue life model of asphalt pavement was introduced to construct general fatigue equations for the asphalt layer of semi-rigid asphalt pavement or ultra-thin pavement subjected to multiple factors, and the correlation of fatigue life with the influencing factors and the most unfavorable point were determined. The results show that the interlayer bonding coefficient, temperature, and axle load all have significant effect on the fatigue life of asphalt layer, but the effect differs at different calculation points. Strengthening the interlayer bonding condition can improve the fatigue life of the asphalt layer: at the most unfavorable point, when the interlayer bonding coefficient is improved from 0.5 to 0.7, the fatigue life is increased by 13.6 times.

Evaluation of Asphalt Concrete Pavement Based on Passenger Ride Comfort Level

WANG Feng, ZHANG Jinxi

2014, 27(4): 687-692. doi: 10.3969/j.issn.0258-2724.2014.04.020

[Abstract](863)

Abstract:
In order to provide a theoretical basis for the ride comfort level evaluation, daily management, and maintenance of asphalt concrete pavement, the performance parameters and three-directional acceleration data of highway pavements were measured indoors and outdoors. Using these data, the relationship between the mean square of weighted acceleration and the pavement performance was studied. A linear regression equation that reflects the relationship between the root mean square of weighed acceleration, speed, and roughness was obtained by fitting 214 groups of experimental data. In addition, the outdoor experimental results were verified using a driving simulator. The results show that the root mean square of weighed acceleration is strongly correlated with roughness, moderately correlated with the speed, and weakly correlated with the dynamic friction coefficient. Given a certain dynamic friction coefficient, the ride comfort level of an asphalt concrete pavement reduces with its roughness and driving speed increasing. When the roughness is 1.35 and 3.05 mm/m, the maximum speed with an appropriate ride comfort level is 124.1 and 88.7 km/h, respectively.

Coupled Vibration Characteristics of Flexible Car Body and Equipment of EMU

SHI Huailong, WU Pingbo, LUO Ren

2014, 27(4): 693-699. doi: 10.3969/j.issn.0258-2724.2014.04.021

[Abstract](941)

Abstract:
To study the coupled vibration between a flexible car body and its suspended equipment, a rigid-flexible coupling dynamic model of high-speed electric multiple units (EMUs) was established taking into account the flexible modes of the car body. The swept frequency excitation method was used to analyze the influence of suspension parameters on the system vibration, such as the equipment mass, suspension frequency, damping, and mounting position. Then, the vibration characteristics of the system were studied under the interplay between various parameters. The results show that the flexible vibration could be reduced significantly by the elastic suspension of equipment compared to the rigid suspension case. The system showed a good vibration absorber performance if the heavy equipment was suspended elastically close to the car body center, while it had a little effect on the flexible vibration reduction if the equipment mass was lower than 1.0 t or more than 6 m apart away from the center. Furthermore, the damping ratio of the elastic suspension should remain in a certain range from 5% to 30%. In addition, a laboratory test was conducted on a vehicle rolling and vibration test rig. The test results show a good agreement with the simulation ones: the elastic suspension can improve the riding comfort obviously, and the effect increases with the running speed increasing, with a maximum reduction of about 15% at a certain speed.

Analysis of Wheel/Rail Impact Induced by Wheel Flats

WANG Yijia, ZENG Jing, GAO hao, LUO Ren

2014, 27(4): 700-705. doi: 10.3969/j.issn.0258-2724.2014.04.022

[Abstract](930)

Abstract:
In order to study the dynamic issues induced by wheel flats for high speed trains, a dynamic model and new/worn wheel flat models were developed using the multi-body theory and the equivalent track excitation method. The simulation method considering the change of wheel radius was applied to simulate the wheel flat and analyze the wheel/rail impact caused by wheel flats. The results show that the behaviors of wheel-rail impact forces caused by new and worn wheel flats are different: the impact force caused by a worn flat increases with the train speed increasing, and is significantly larger than that by a new flat at high speeds. When the running speed of the train is larger than 200 and 250 km/h, the length of the wheel flat should be limited within 35 and 30 mm, respectively.

Algorithm for Detecting Modular Structures and Diagnosing Hub Sections in Urban Road Network

HU Yucong, CHEN Haiwei

2014, 27(4): 706-711. doi: 10.3969/j.issn.0258-2724.2014.04.023

[Abstract](875)

Abstract:
In order to detect the complexities of topology and discover the key road sections in urban road network, the clustering feature of urban road network was analyzed by modular structure theory, and a GN-T algorithm was proposed for dividing the modular structures and diagnosing hub sections in the urban road network. By iterative removal of links with the maximum intermediate values from road network, this algorithm split the whole network into modular structures and found out hub sections. In addition, an improved modularity function was also proposed for determining the optimal number of modular structures in the urban road network. As a case study, the urban road network of Wuchang city was used to test and verify the algorithm. The results show that the maximal value of modularity in the network is 0.41, indicating that the urban road network of Wuchang city possesses obvious modular structure characteristics. In addition, the hub sections derived from the algorithm is consistent with the reality. All these demonstrate the effectiveness and practicability of the GN-T algorithm.

Model and Approximation Algorithm for Dynamic Wagon-Flow Allocation Based on Greedy Strategy

GUO Rui, GUO Jin, SU Yuebin, MA Liang

2014, 27(4): 712-719. doi: 10.3969/j.issn.0258-2724.2014.04.024

[Abstract](1002)

Abstract:
To develop a method for the intelligent generation of dynamic wagon-flow allocation, which can search and solve efficiently and timely perform adjustment, the multi-stage decision model was built based on greedy algorithm. By dividing the decision process into several stages of the marshaling sequence, a division method was proposed for dynamically sorting intervals in each stage according to Δti, which is the value of the difference between the final formation time and the earliest sorting time mod standard break-up operation time. For each sorting interval, with train demand used as matching targets, five optimal selection algorithms of sorting trains were designed on the basis of different rules and strategies. The decision variables in each stage were queued to form the final sequence of sorting trains. Comparison tests of 8 groups show that simple rules and strategies can not guarantee a desirable solution, and whether a selection algorithm of matching targets is suitable depends on the number of sorting intervals and the selection strategy of sorting trains. Using the R_PPCD2-based algorithm (R_PPCD2 is a strategy which selects the sorting train by the matching degree of wagon-flow's orientation between the current stage and other remaining stages), a high-quality approximate solution for this type of NP-hard problem can be found in 2 s by proper adjustment of parameters such as break-up operation time, marshalling operation time, departure operation time.

Evaluating Performance of Non-intrusive Indicators on Drowsy Driving Detection

XU Chuan, WANG Xuesong, CHEN Xiaohong

2014, 27(4): 720-726. doi: 10.3969/j.issn.0258-2724.2014.04.025

[Abstract](988)

Abstract:
To detect the drowsiness state of the driver more accurately, a high-fidelity driving simulator was adopted to collect the driving behavior and eye movement data of drivers, and questionnaires were used to collect their subjective sleepiness scales. Based on these data, 23 non-intrusive indicators were developed. The indicators were evaluated from the aspects of their correlation with drowsiness, binary classification performance, sensitivity to road alignment, and individual homogeneity; and then ranked in terms of comprehensive performance. The results show that the percentage of eyelid closure time (PERCLOS) has the highest correlation (0.443) with the Karolinska sleepiness scale (KSS). The best binary classification performance of eye movement and driving indicators lies on PERCLOS and the lateral position standard deviation (LPSD). For eye movement indicators, the difference between straight line and curve is lower than 20%. When KSS is 7, all the indicators show significant individual difference except the percentage of lane crossing time of vehicle center. The top three non-intrusive indicators with the best comprehensive performance are PERCLOS, LPSD, and the average lateral speed during lane departure.

Airline Fleet Robust Optimization Approach under Stochastic Demand with Route Network Effects

WANG Yu, ZHU Jinfu, GE Wei

2014, 27(4): 727-733. doi: 10.3969/j.issn.0258-2724.2014.04.026

[Abstract](961)

Abstract:
In order to solve the problem of network effects under uncertain passenger demand in route network, the itinerary-based optimization model for passenger-mix problem was incorporated into airline fleet planning problem. According to the optimization method for fleet capacity allocation, the number of aircrafts in each fleet type, the frequencies of different type of aircrafts flying on each leg, and the number of spilling passengers on each itinerary were regarded as decision variables. The limitations including the maximum passenger demand on each itinerary, available flying frequency on each flight leg, and available block time of each fleet type were considered as constraints. A robust optimization model for airline fleet planning under demand uncertainty was constructed by using the "quantitative share index" to calculate the passenger spilling recapture rate. After generating a discrete scenario set of passenger demand under the route network environment, the scenario aggregation algorithm was employed to solve the proposed model. Simulation results of an empirical example indicate that the fleet planning cost gained from this proposed model is reduced by 1 670 700 Yuan compared to the traditional model. The stochastic planning solution to fleet planning cost in 3 different scenarios decreases by 198 800 Yuan, 210 200 Yuan, and 175 500 Yuan, respectively, as opposed to the deterministic solution to the minimum stochastic expectation values.

Real-Time Adjustment Strategy of Aircraft Taxiing Routes for A-SMGCS

TANG Yong, HU Minghua, HUANG Rongshun, LIU Weidong, WU Honggang, ZHU Xinping, XU Zili

2014, 27(4): 734-740. doi: 10.3969/j.issn.0258-2724.2014.04.027

[Abstract](875)

Abstract:
Adjustment of airport taxiing routes in operation phase of aircrafts needs a large amount of calculation, which makes it difficult to meet the real-time requirements for A-SMGCS (advanced surface movement guidance and control system). In order to resolve this problem, a colored taxiway-oriented Petri net model was built and a method of aircraft taxiing routes adjustment was proposed. The method abstracted taxiing routes to the visiting priorities of aircrafts on a road section. The delayed aircrafts were punished by decreasing the priorities to visit the road section. To change priorities of aircrafts might lead to two kinds of conflicts: head-on conflicts and circular wait conflicts. Sufficient condition and priority change strategy of aircrafts conflict-free taxiing were proposed to solve those conflicts by analyzing the special structural characteristics of cycle chains and circuits of the colored taxiway-oriented Petri net model. An application example shows that the proposed method can avoid conflicts in aircrafts taxiing routes adjustment. The computation time is less than 10 s, which meets the planning time requirements of A-SMGCS. The control rules are simple, effective and suitable for real-time control.

Bifurcation Control of Mechanical System with Periodic Coefficients

ZHENG Xiaowu, XIE Jianhua

2014, 27(4): 741-745. doi: 10.3969/j.issn.0258-2724.2014.04.028

[Abstract](755)

Abstract:
In order to control the bifurcation behavior at the equilibrium point of the differential system with periodic coefficients losing its stability, the methods for bifurcation control for the dynamical system with constant coefficients, such as using the linear controller, parameter method, and translation, were applied to a mechanical system with periodic coefficients by the Floquet-Lyapunov theory. Then, the related controllers were designed, and its validity in controlling the bifurcation behavior at the equilibrium point was tested through numerical calculation. The results show that translation is invalid to control the Flip and Hopf bifurcations at the equilibrium point in mechanical system with periodic coefficients. When a 2-periodic point is generated by the period-doubling Flip bifurcation at the unstable equilibrium point, either of the linear controller and the parameter method can be used to control the 2-periodic point back to a 1-periodic point. When a Hopf circle is generated by Hopf bifurcation after the equilibrium point loses its stability, the linear controller and the parameter method are all effective for controlling the Hopf circle to a 1-periodic point.

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2014 Vol. 27, No. 4